Beam compass carriage



March 3o, 1937. H. O. LETZERICH 2,075,523

BEAM COMPASS CARRIAGE Filed May l, 1936 lNvENToR Harry O. Lezer'lchPatented Mar. 30, 1937 UNITED STATES PATENT. OFFICE 6 Claims.

This invention is an improvement in the carriage of a beam compass usedin all classes of draftsmanship for describing circles of a largerradius than can conveniently be drawn by the usual smaller instrumentsand the improvement is intended to facilitate the accuracy of thedrawing.

There are two general divisions into which these instruments may bedivided, one of considerable refinement and cost and which is fittedwith some sort of Vernier or adjustment to permit the greatest accuracyand the other type, whereby a rougher and much cheaper instrument may beused but which permits fairly accurate work to be done.

The object of this invention is to further refine the last named type sothat a greater measure of accuracy can be obtained at the lower cost ofthe simpler and cheaper beam compass.

Other objects and advantages will be more apparent to those skilled inthe art from the following description of the accompanying drawing inwhich:

Fig. 1 is a side elevation showing the entire beam compass assembledready for use;

Fig. 2 is a perspective view of my improved carriage;

Fig. 3 is a longitudinal section through one of the carriages taken onthe line 3 3 of Fig. l;

Fig. 4 is a modification of the carriage, the section being taken on aline similar to line 3 3 of Fig. l.

The assembled beam compass is shown generally at I, Fig. l, the beam 2being of any convenient length and preferably of wood, although anyother suitable material may be used. Carriages 3 3, located at eitherend of the beam, are identical, and hence the description of one willsuffice for both. The carriage is made of relatively thin sheet metalhaving the property of springing or of being slightly resilient, this inorder that carriage bed plate wings 6 6 at each side of the bed plate Imay grip or clamp the beam 2 with sufficient pressure to preventlongitudinal movement thereon while drawing a circle or arc and yet beadapted to yield to effect longitudinal adjustment in order to changethe distance between the center point and the pen (or pencil points) 4and 5 when a different radius is desired. The wings are substantially ofconcave shape partially enclosing the beam.

So far this describes the carriage as extensively used heretofore. Asthe design ofthe center point and pen and pencil points is old, theyform no part of this invention and hence need not be further mentioned.

The above mentioned points are held in Vf holders 8 attached to the bedplate Iypreferably by welding or brazing and are clamped tightly bysprings 9 riveted or brazed to bed plate I, this spring being clampedagainst the points 4 and'5 by a knurled nut I 0 threaded on a screw I I,this nut being attached to the bed plate 6 preferably by thread andbrazed or soldered to prevent rotation. By attaching the V-holdersdirectly to the bed plate, I am able to accomplish ymany of thedesirable results herein set forth lsuch-,as nicety of adjustment withminimum possibility of misalignment o-f the pen or pencil and withminimum effort.

The spring 9 has an upturned lip or thumb lug I2 at the end of the bedplate 1, this feature being one of the improved aspects of the inventionas it is intended to provide an enlarged surface against which the thumbcan exert the slight pressure required when shifting the carriage to anew radius. Heretofore it has been necessary to apply such pressure tothe relatively sharp edges of the bed plate 'I, the spring 9 in mostcases not extending to the said edge of plate 'I with the result thatthe delicacy of pressure required for a minute adjustment could notalways be obtained. Hence several movements to and fro might be madebefore the nal setting was obtained.

Another improvement is the improved manner of attaching the V-holders 8to the bed plate 1 instead of to the spring 9 as heretofore. This newmode of application stiffens the bed plate l at the opposite endfromthat to which an extended lip I2 of the spring 9 is attached, thuspermitting the wings 6 6 to yfunction to the best advantage andirrespective of any bending or slight springing of the bed plate 'I. Theresult is that movement of the carriage by pressure of the thumb on lipI2 will be resisted by a very even and regular pressure of the wings 6 6on the beam 2.

Still another feature is an improved relation of a bearing flange I3 onthe clamping nut IIJ, which flange overlies the center of points 4 and 5so as to insure that the thrust of the nut and screw is positivelyapplied to the points 4 and 5 through spring 9 held within the V-holders8. This furr ther makes for rigidity in case it is desired to adjust thesetting of the beam without removing the center point from the draftingboard. Fig. 4 shows a modification in which the thumb lug I2 is formedintegrally with bed plate "I, Also,

the V-holder is formed from a reversely bent extension 8 of the bedplate. The construction and function of lug I2 and the V-holder 8 arethe same as that shown in Fig. 3. It is understood that any usual meansof attaching the various parts together such as riveting, brazing,soldering, welding or by threaded connections may be used as Well as theusual modifications covered by the intent and spirit of the invention asdefined by the claims appended hereto or as substantially shown in thedrawing and specification hereof.

I claim:

1. A beam compass pointer carriage comprising, in combination, a fiatbed plate with substantially concave integral Wings at each side thereoffor engaging the beam, and a V-shaped pointer holder attached to andsupported directly by said bed plate.

2. The combination set forth in claim 1 further characterized in thatthe V-shaped holder is secured near one end of the bed plate and aclamping spring overlying the V-holder is attached to the opposite endof the bed plate.

3. The combination set forth in claim l further characterized in thatthe V-shaped holder is secured near one end of the bed plate and aclamping spring overlying the V-holder is attached to the opposite endof the bed plate, the end of the clamping spring Which is attached tothe bed plate, having a bent extension` forming a lip extendingoutwardly at approximately to the bed plate.

4. The combination set forth in claim 1 further characterized in thatthe V-shaped holder is secured near one end of the bed plate and aclamping spring overlying the V-holder is attached to the opposite endof the bed plate, the end of the clamping spring which is attached tothe bed plate having a bent extension forming a lip extending outwardlyat approximately 90 to the bed plate, a bolt secured in the bed plateand extending through the clamping spring, and a clamping nut on saidbolt having a bearing flange resting on the clamping spring to tighten apen or pencil in the V-holder.

5. The combination set forth in claim 1 further characterized in thatsaid V-holder is formed from a reversely bent extension of one end ofthe bed plate, a clamping spring extending over the V- holder andattached to the bed plate, and a bolt and nut for clamping said springand V-holder together, said clamping nut having a bearing flange restingon said clamping spring.

6. The combination set forth in claim 1 further characterized in thatthe V-shaped holder is secured near one end of the bed plate and aclamping spring overlying the V-holder is attached to the opposite endof the bed plate, an upturned lip is formed on the end of the bed plateto which the clamping spring is fastened, from a reversely bentextension of the bed plate, a bolt secured in the bed plate andextending through the clamping spring, and a clamping nut on said bolthaving a bearing flange resting on the clamping spring to tighten a penor pencil in the V-holder.

HARRY O. LETZERICH.

